Color sensitive photographic plate and method of producing same



" Oct. 10, 1939. FRIEDMAN r AL 2,175,836

COLOR SENSITIVE PHOTOGRAPHIC PLATES AND METHOD or PRODUCING- SAME Filed March 11, 1957 FR-EMULSION F- CARRIER i 4 f SIIRFGIEEN No PENETRAT'ON IESENsITIZING DYE I MUl-SION CARRIER I 1' wA'rER-ALcoI-Io I. BATH BELOW Room TEMPERATURE To PREVENT PEN E- TRATION WITH OR WI'IHOUT A YE I.I ow I FI L'I ER DYE. LIMITE D PENE" TRATION OF RED E-IuI sIoN ORGREEN SEN- SITIZING DYE. fmcmmm WATER-ALCOHOL sow-non OF A YELLOW FILTER DYE' LIMITED PENETRAT- ION OF REDORGREEN SENSITI'LING DYE FILTER DYE EMULSION CARRIER INVENTOR. JOSEPH S. FRIEDMAN ATTORNEYS Patented Oct. 10, 1939 COLOR SENSITIVE PHOTOGRAPHIC PLATE AND METHOD OF PRODUCING SAME Joseph S. Friedman, Brooklyn, and Arthur Bruck, New York, N. Y., assignors to Color Processes, Inc., New York, N. Y., a corporation of New York Application March 11, 1937, Serial No. 130,304

4 Claims.

The present invention relates to the color sensitive photographic plates and methods of producing the same.

Photographic plates are usually composed of 5 a carrier, which may be of paper or opaque material as in the case of positive prints or a transparent plate or film of glass, nitro-cellulose, cellulose acetate, and so forth, in connection with negative prints.

On these carriers is deposited a layer of an emulsion containing a light sensitive silver salt or halide, such as silver bromide or silver iodide, emulsified in a water soluble colloid, such as gelatine, and so forth.

These silver salt emulsions are usually excessively sensitive to blue or violet light, some of said violet light being outside of the visible range and as a result, the pictures produced thereon are photographed with different value particularly 9 as to light and darkness or the value of the different colors than the object or subject being photographed actually appears to the human eye.

It is often desirable to control the emulsionso that the silver salts therein will be more nearly sensitive to other primary colors than blue or violet, but as a general rule, it has not been possible to most satisfactorily prepare an emulsion which would be selective to one primary color,

such as red or green and produce an image corresponding to such color.

It is, therefore, among the objects of the present invention to prepare a photographic plate which will be selectively sensitive to one of said primary colors, to which the photographic plates are not ordinarily sensitive, such as red or green with assurance that an image may be developed or obtained which will correspond substantially exactly to the red and green or yellow values of the object being photographed.

It has been found that certain dyes, particularly having a conjugated chain of double carbon bonds are able to form compounds or complexes with the silver salts in an emulsion which has been deposited upon a suitable carrier which complexes are sensitive to red or green.

However, considerable difliculty has been experienced in properly compounding'or combining these sensitizing organic compounds with the silver salt emulsion. Where the emulsion and carrier are immersed in an aqueous solution of the color sensitizing agent or dye, it is not possible readily to control the diffusion of the dye into the emulsion even where there is a most careful control of the concentration, temperature and time.

minute layer of the sensitizing organic compound or dye is deposited upon the surface of the emulsion, that such color may be caused to diffuse with great control and desired uniformity if the.

coated film is subsequently placed in an aqueous bath or in an alcohol-water solution.

According to the preferred method of performing this invention, a red sensitizing or green sensitizing organic compound or dye is placed in an alcohol solution of sufiiciently high concentration not to be absorbed or diifused into the emulsion. Then, subsequently after removal and drying to cause a thin layer of the sensitizing dye to dry upon the surface of the emulsion, the emulsion is then dipped into water or a water alcohol solution which causes the dye to undergo a controlled difiusion into the emulsion to the desired depth.

In commercial practice, it is often most desirable not merely to photograph only the green, blue or red values, but to obtain images of the same object in each of these values to enable subsequent reproduction of a colored photograph by photographic or printing processes, and it is a further object of the present invention to prepare a photographic plate which will give readily separable images representing at least two of the primary colors above mentioned, as for example, red and blue or green and blue.

This last mentioned object is attained by immersing the plate after it has been coated with a thin layer of the red or green sensitizing dye v in an aqueous bath containing a filter dye.

The red sensitizing dyes may be plnacyanol, ,naphthocyanine, neocyanin, kryptocyanine, and so forth, which may be used singly or in mixtures in very small concentrations less than 0.1% in alcohol solution. The alcohol used may be isopropyl alcohol, also known as petrobol ethyl alcohol or other readily volatile, preferably not readily inflammable or toxic organic solvents.

The green sensitizing dye may be pinachrome or orthochrome T or a similar dye, which may be used in lieu of the red sensitizing dye and in the same concentrations.

The filter dye may be any blue absorbing dye, such as auramine, tartrazine, rapid filter yellow, quinollne yellow and so forth, the filter dye preferably being utilized in a water-alcohol bath used for-causing diffusion of the red or green sensitizing dye. b

To give one typical example of a method of accomplishing the above objects, two baths are prepared, one composed of 30 cc. of 0.1% pinacyanol solution in 98% isopropyl alcohol, diluted to one liter with 98% isopropyl alcohol (known as Petrohol) and a second compound of 15 cc. of a 1% alcoholic solution of auramine diluted to 1 liter with a. 20% isopropyl alcohol water solution.

The blue sensitive plates, such as the EK 33, Hammer white label, Cramer Alpha. and so forth, are bathed in the first bath for two minutes at room temperature, and then dried. This leaves a film of sensitizing dye upon the surface of the plate. No penetration into the emulsion layer takes plate in this operation and hence no sensitization whatever is achieved at this stage.

After drying, the plates are bathed for 45 seconds in the second bath at 40 F. This low temperature is chosen to control the amount of yellow dye or auramine that is absorbed by and diffused through the emulsion layer. The diflusion of the auramine will have no effect upon the simultaneous diffusion of pinacyanol into the emulsion layer.

The auramine will penetrate through the emulsion to the carrier so that when the carrier is faced toward the lens of a camera, the blue or violet will be all absorbed in the portion of the emulsion adjacent said carrier.

The pinacyanol, on the other hand, although it may dissolve slightly into the water bath, will principally diffuse into the emulsion away from the carrier and combine with the silver salt forming a zone of red sensitivity.

The degree to which the red sensitivity penetrates into the depth of the emulsion is determined by the amount of penetration of the pinacyanol which causes silver halide to become red sensitive by reaction with it. Ordinarily, the

water alcohol solution may be compounded to cause a controllable diffusion to take place when a photographic plate is treated therein.

With the present process, however, this diffusion of red or green sensitizing dye need not be rigidly controlled and will not be substantially affected by variations in pH, humidity or gelatine characteristics.

Instead of alcohols in the .first bath, it is also possible to use other volatile solvents, which will avoid diffusion of the red or green sensitizing dye, such as for example, hydrocarbons as benzene or toluol, ethers, ketones, esters and so forth.

The sensitizing agent in such a volatile liquid solvent does not and cannot penetrate into gelatine layers.

The green or red sensitizing dyes, above mentioned, have great avidity for the silver halides and their presence in concentrations of 1 to 1,000,000 is still sufficient to cause the sensitizing reaction to take place. Therefore, the first bath should only be of such strength that only sufficient sensitizer, as pinacyanol will be deposited upon the surface of the gelatine layer to react with the silver halide in the upper half of the emulsion layer away from the glass or cellulose carrier.

' Reaction between the two takes place and in this manner the pinacyanol is completely used up during its penetration into the upper part of the emulsion layer.

Of course, the red sensitizing dye, pinacyanol may be replaced by others such as naphthocyanine, neocyanin, kryptocyanine, and so forth. Also, instead of. sensitizing for the red, it is possible to sensitize for the green using such dyes as Pinachrome, Orthochrome T, and so forth.

After sensitization to red or green is completed, the plate is loaded into a plate holder in the reverse manner to the customary one so that the carrier side or bottom of the emulsion layer faces the lens. The plate may then be exposed. After exposure, the plate is developed in an ordinary developer, washed thoroughly in running water and then completely densensitized as by bathing for ten minutes in a desensitizing bath, containing an acidified solution of potassium iodide and pinacryptol green, safranine, or other desensitizing dye. After a brief rinse the plate is dried.

When observed on either side it will be seen that plate contains a black silver image imbedded in a white opaque or red opaque body. It will also be found that the images when viewed through the carrier side and through the emulsion side, differ from each other in that the densities which represent the blue primaries are confined to the carrier side while those representing the red or green densities are confined to the emulsion side.

The reason for this is readily apparent. The blue rays enter the lens and are focused upon the back of the plate sensitized. The blue rays in passing through the emulsion react with the silver halide to form the latent image corresponding to the blue values. As they progress through the emulsion layer they are absorbed by the silver halides and by the yellow filter dye so that by the time they reach the upper half of the emulsion they are completely absorbed. No blue rays, therefore, penetrate into upper half of the emulsion layer which has been made red or green sensitive by the above treatment.

The red or green rays pass through the bottom half of the emulsion layer, which is not sensitive to the red or green rays, without absorption. When the rays penetrate to the upper half of the emulsion layer they reach the silver halide salts that have previously reacted with the sensitizing solution and so are red or green sensitive. There the latent image due to the red or green rays is formed.

In the drawing is shown diagrammatically the various steps according to which the above process may be carried out, the drawing illustrating the successive changes. in the plate as it is subjected to the different steps in the treating process.

The two latent images may be developed by an ordinary developing solution into black negative images, which by further treatment may be made permanent as black images imbedded in opaque white or red reflective surfaces or they can be converted into white opaque silver iodide imbedded in-black opaque non-reflective surfaces as described in the copending application for patent, Serial No. 130,306, filed March 11, 1937.

These separate images may then be photographed from opposite sides of the plate to give pictures of the object in two primary color values, or the silver image may be oxidized and replaced by a coloring substance to give the color values of the images, or the plate may be fixed in which case the two images will be superimposed upon a transparent glass or film carrier and the object may be observed as photographed in two primary colors.

When a filter dyeis not employed and where an image in green or red values alone is to be obtained, the blue light is preferably filtered out before exposure of the red or green sensitized plate, eitheron the carrier or emulsion side.

The sensitized elements produced according to the process of the present invention may also be used as a front element of a bi-pack if desired, as described in co-pending application, Serial No. 130,305 filed March 11, 1937.

If it is desired to obtain a combined red and green value image in the element of the present application, both the green and red sensitizing dyes may be dissolved in the first bath.

The important feature of the present invention resides in first forming a surface coating of a color sensitizing dye upon the face of a silver salt emulsion without penetration of said sensitizing dye into the emulsion and without sensitization of the emulsion.

The solution which is utilized to form the surface coating should contain a sufficient concentration of volatile solvent or alcohol to prevent penetrationof the dye into the emulsion. Then, the emulsion is placed in an aqueous bath which will cause the dried surface layer of the sensitizing dye to penetrate into and to sensitize the silver salt emulsion. This two step operation has been found to be most important and to give most satisfactory results.

It is to be understood that the invention is not intended to be restricted to any particular example, composition or proportions, or to any particular application, or to any specific manner of use or to any of various details thereof, herein described, as the same may be modified in various particulars or be applied in many varied relations without departing from the spirit and scopeof the claimed invention, bodiments herein described merely showing some of the various features entering into the application of the invention.

What is claimed is:

1. A method of producing multi color sensitive stratification of the light sensitive emulsion on a photographic plate having a transparent carrier, said plate to be exposed with the carrier toward the source of light and to produce the image in one color value adjacent the carrier and in another color value away from the carrier which comprises providing a plate composed of said transparent carrier coated with a blue sensitive gelatine emulsion of an insoluble silver halide, immersing said plate in a substantially nonaqueous organic solvent solution of a color sensitizing dye, which dye will sensitize the emulsion to one of the primary colors other than blue, said solution being of such a character as not to swell orpenetrate the emulsion, said solution containing a sufficient concentration of organic solvent to prevent any substantial penetration of the dye into the emulsion, removing the plate and drying to form a substantial non-penetrating surface coating of thesensitizing dye upon the emulsion without substantial sensitization of the emulsion, and then treating the dried plate with an aqueous solution of an organic solvent to cause a slight swelling and to cause a limited diffusion of the deposited surface coating of the sensitizing dye into the outer portion of the emulsion without penetrating the portions of the emulsion adjacent the carrier, whereby upon exthe practical emposure of said plate with the carrier facing the source of light the portion of the emulsion adjacent the carrier will reproduce the image in blue values while-the portion of the emulsion away from the carrier will reproduce the image in values corresponding to the sensitization obtained by the sensitizing dye.

2. A method of producing multi color sensitive Stratification of the light sensitive emulsion on a photographic plate having a transparent carrier, said plate to be exposed with the carrier toward the source of light and to produce the image in one color value adjacent the carrier and in another color value away from the carrier which comprises providing a plate composed of said transparent carrier coated with a blue sensitive gelatine emulsion of an insoluble silver halide, immersing said plate in a substantially nonaqueous organic solvent solution of a color sensitizing dye, which dye will sensitize the emulsion to one of the primary colors other than blue, said solution being of such a character as not to swell or penetrate the emulsion, said solution containing a suflicient concentration of organic solvent to prevent any substantial penetration of the dye into the emulsion, removing the plate and drying to form a substantial non-penetrating surface coating of the sensitizing dye upon the emulsion without substantial sensitization of the emulsion,

and then treating the dried plate with arr aqueous solution of an organic solvent to cause a slight swelling and to cause a limited diffusion of the deposited surface coating of the sensitizing dye into the outer portion of the emulsion without penetrating the portions of the emulsion adjacent the carrier, whereby upon exposure of said plate with the carrier facing the source of light the portion of the emulsion adjacent the carrier will reproduce the image in blue values while the portion of the emulsion away from the carrier will reproduce the image in values corresponding to the sensitization obtained by the sensitizing dye, the organic solvent in the first solution consisting of isopropyl alcohol which alcohol is utilized in over concentration in the solution 'of thesensitizing dye and the organic solvent in the second solution consisting of isopropyl alcohol and the alcohol'being utilized in about 50% concentration in the last mentioned treatment to cause limited diffusion and penetration.

3. A method of producing multi color sensitive stratification of the light sensitive emulsion on a photographic plate having a transparent carrier, said plate to be exposed with the carrier toward the source of light and to produce the image in one color value adjacent the carrier and in another color value away irom the carrier which comprises providing a plate composed of said transparent carrier coated with a blue sensitive gelatine emulsion of an insoluble silver halide, immersing said plate in a substantially nonaqueous organic solvent solution of a color sensitizing dye, which dye will sensitize the emulsion to one of the primary colors other than blue, said solution being of such a character as not to swell or penetrate the emulsion, said solution containing a suflicient concentration of organic solvent to prevent any substantial penetration of the dye into the emulsion, removing the plate and drying to form a substantial non-penetrating surface coating of the sensitizing dye upon the emulsion without substantial sensitization of the emulsion, and then treating the dried plate with an aqueous solution of an organic solvent to cause a slight swelling and to cause a limiteddiflusion of the '1 deposited surface coating of the sensitizing dye into the outer portion of the emulsion without penetrating the portions of the emulsion adjacent the carrier, whereby upon exposure of said plate with the carrier facing the source of light the portion of the emulsion adjacent the carrier will reproduce the image in blue values while the portion of the emulsion away from the carrier,

will reproduce the image in values corresponding 10 to the sensitization obtained by the sensitizing JOSEPH S. FRIEDMAN. ARTHUR BRUCK. 

